Angle plates are commonly utilized to form rigid, connectable corners in HVAC ducting. Each duct is provided with a channel flange at one or more ends at the corners of a generally rectangular section. The angle plates are placed in the channel at the corners of opposing flanges of opposing duct sections and are bolted or clipped together, forming a joined section of ductwork. The process of insertion of the angle plates into the flanges, as well as the general design of the angle plates are more fully described in Daw, et al., U.S. Pat. Nos. 9,377,213; 9,545,695 and United States Patent Application Publication No. 2016/0297040.
Angle plates are well known in the field of HVAC duct connection. Each are generally right angular, having two leg portions joined at an apex. In early embodiments, as exemplified in Mez, U.S. Pat. No. 3,712,650, the angle plates were inserted longitudinally into a preformed cavity perimetrically located at the leading edge of a duct flange. This is illustrated in FIGS. 1 and 2 of Mez. The angle plate is manually inserted into each of the perpendicularly located adjacent cavities at each corner of the generally rectangular duct by the corresponding leg portions. A bolt hole is provided at the apex of the angle plate to facilitate the joining of two duct sections at each corner by passing a bolt or other fastener through a first angle plate bolt hole to a corresponding angle plate bolt hole affixed to the second duct section.
Later improvements in the art of duct flange joinder included the development of automated angle plate insertion devices, as exemplified in Goodhue, U.S. Pat. No. 5,342,100. Goodhue discloses an angle plate and a device for installing angle plates in the corners of HVAC ducts. The angle plates so described are configured so as to be automatically fed to the installation device through a supply hopper and a stack of angle plates is inserted in the hopper for such automatic feeding. This is best illustrated in FIGS. 9 and 15 of Goodhue.
Originally, angle plates were manually assembled into stacks and placed into the supply hopper. Various tools, both commercial and improvised, were developed to assist in the organization and stacking of the angle plates to improve efficiency in unpacking and loading the angle plates. Many of these incorporated the use of the bolt holes in the angle plates and elongated prongs to assemble stacks. However, rotation of the angle plates about the prong axis still required significant manipulation of the angle plates by hand, decreasing efficiency. In light of the need to continuously fill the supply hopper of such automated installation devices and the limitations of manual stacking, a number of embodiments of prepackaged angle plate stacks have been proposed.
Prepackaged stacks of angle plates must incorporate at least two design limitations. They must resist rotation and lateral displacement of the angle plates relative to each other in the stack and must facilitate easy insertion of the angle plates into the supply hopper and removal of the packaging without disturbance.
Initially, a cardboard sleeve was proposed in Daw, et al., U.S. Pat. No. 9,027,376, in which the angle plates were loaded in stacks of preselected amounts. The sleeve, as illustrated in FIGS. 5 and 6 of Daw, was sized to conform to the right-angle perimeter of the angle plates and incorporated a lid which facilitated the removal of the sleeve from the angle plates once in the supply hopper was loaded. The sleeve was also adapted to fit within the confines of the supply hopper prior to unloading.
A more common embodiment of the sleeve stack incorporates plastic or other straps extending longitudinally along the stack length. Use of the straps, rather than the box packaging is simpler and more economical. Use of straps is exemplified in Daw, et al., U.S. Pat. No. 9,545,695. FIGS. 18-19A, inclusive, illustrate several embodiments which include a variety of straps and conformations. Notably, FIG. 18 includes two straps, one on each leg portion, while FIG. 18A illustrates four straps, two on each leg portion. FIG. 19 illustrates the use of a single strap spanning both leg portions and forming a hypotenuse of a right triangle with the leg portions of the angle plates.
Commercial use of the various package and strap embodiments has identified certain limitations in the assembly and maintenance of the stacked angle plates. Many embodiments of the supply hopper are enclosed, at least partially, reducing visibility of the angle plates therein. Moreover, access to the straps may be obstructed by the hopper side walls and supports, making removal of the straps difficult. Many hopper embodiments, however, include an open area at the apex of the stack of angle plates. The only known single strap embodiment, as illustrated in FIG. 19 of Daw '695, has proved to be unstable with respect to consistent transport, loading and unloading of stacks with respect to bulk packaging and insertion into the assembly devices.
What is lacking in the art is a single strap embodiment which provides appropriate resistance to rotational and lateral movement of the plates, while facilitating easy removal while in the supply hopper. The development of alternative one-strap embodiments has proven to be more challenging that mere optimization of the parameters for assembling an angle plate stack, as rotational and lateral forces typically cause unintentional spontaneous collapse of the stack absent a particular assembly structure.